So, I am going to be making a Belgian Tripel in the next couple of weeks. I am planning making about 15% of the grain bill be candi sugar. I have only made beers where sugar is less than 10% of the bill and I usually add it in the boil (at the end) with no ill effects.

I know there are differing schools of thought on whether to add these larger amounts of sugar to the boil or in primary. I was reading that yeast will eat the simpler sugars first and their metabolism can actually switch over to that type of sugar, thus not eating the malose barley sugars and causing stuck fermentation.

I am just curious what people's experiences have been with either methods.

I do make yeast starters and just started doing O2 injection into my wort so the yeast should be pretty healthy.

I've never done late sugar additions and have never had a beer fail to attenuate. I think maybe if you're abusing your yeast, underpitching and underaerating, then yea, maybe it could make difference. But I treat my yeast nicely like you do and have done a tripel with 30% sugar and it attenuated fully.

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I can't be arsed to keep up this list of what's in the fermenters, but hey, check out the cool brewery I own!

I too have not had any attenuation issues with sugar in the boil and I don't think 15% would be a problem but if you are concerned you can make a simple syrup, cool to wort temp and add it to the primary as high krausen is almost complete.